The procedure involves a liquid-filled balloon placed in the stomach to make the patient feel more full and eat less. The balloon is inserted via an endoscope down the esophagus to the stomach. Then saline fills the balloon and it remains there for six months.

Illustration of Obera’s weight-loss balloon from FDA documents. The balloon takes up space and causes patients to feel less hungry.

(FDA)

Two companies manufacture the balloons used for the patients who died. Four of the patients received an Orbera Intragastric Balloon System made by Apollo Endosurgery; while one of the patients received a ReShape Integrated Dual Balloon System developed by ReShape Medical Inc.

Both balloon systems were approved by the FDA in 2015.

The FDA says it’s working with both companies to figure out what happened in the three cases where the cause of death is unclear, and the federal agency is warning doctors to closely monitor recent patients.

Back in February, the FDA issued a similar warning to keep an eye on complications from these procedures including the balloons spontaneously overinflating, which can fill the patient’s stomach with fluid, or acute pancreatitis. In these cases, the balloons were removed from the patients.